As a rule of thumb, in a First Person Shooter, the quicker you kill your opponent, the better.
So one hit kills are the absolute fucking bees knees in FPS games, An area in which aliens are rather disadvantaged i must say.
Ok, so its about killing speed is it? Aside from the lucifer cannon, there is only a single alien which is killed in one hit consistently, the dretch. Depending on what the shotgun damage actually is (I think it is slightly below 60, actually), there is a minor possibillity that the basilisk could be one shotted as well. However, hitting such a target with every single shotgun pellet is not common. Now, Its possible, IMO, that one shot kills could favor the humans, and the game still be balanced, but let us, for one moment, pretend that the speed of instant kills needs to be roughly equal on both teams for balance to be achieved.
Now, dretches die in less than a second under normal conditions, so 1-shotting dretches is hardly a huge improvement. If you want to be completely technical, with unlagged, given 100 ping for both players (its not unusual for both players to have ~150 ping, but lets say its 100), that means that the dretch will have exactly 0.2 seconds to live after the human pulls the trigger, so we can quantify exactly how much faster 1 hit kills actually are than other kills (which will take the time the weapon would normally take to kill the alien, plus an additional 0.2 seconds). I have been in a few situations in which this mattered, and both the human and my dretch died simultaneously, with no one else around.
There are no other one shot kills besides the lucifer cannon. Now, 160cr is about equivalent to an evo, give or take a dozen credits depending on how you measure this (you can't, and it isn't reasonable to do so). As far as one hit kills are concerned, the humans and the aliens are roughly equal on this matter, except for the lucifer canno.
However, the lucifer cannon, in general, *does not* kill aliens instantly, except dretches. There are two main factors that contribute to this, the lucifer cannon charge time, and the lucifer cannon's shot speed. The shot speed of the lucifer cannon is huge here. Firstly, it limits the effective range of the lucifer cannon, given an opponent who will dodge. Secondly, it means that an "instakill" will take some time to complete, up to a second, given a resonable range. The charge time is also very important. The human has to know that the alien is coming, and when. To ambush an alien, the human has to know a lot more about the surrounding situation than an alien, who has a radar that updates constantly, and enough mobility, to make the human radar of limited use, given the degree of awareness required (although definitely not useless). Furthermore, the lucifer cannon makes a beeping sound when it is ready to kill a dragoon. If an alien is ambushed, it is in most cases, the aliens own damn fault. If the alien is aware of the lucifer, and holds back, the alien now has a few seconds of relative safety to approach the human. If at this point the alien is killed, it is far from instant. If the human is unaware of the alien, the human will have to spend the first few seconds charging as shot, also eliminating any advantage of killing speed.
So if you don't like dretches I understand (although I personally really enjoy dretching against stage 1 humans), but your claim that 1 hit kills are a problem because it allows the humans can kill the aliens so much faster, and the aliens have to spend a lot to prevent this, I do not understand your reasoning. Aliens have to spend exactly 1 evo to prevent themselves from being instakilled. And I think you are crazy if you are going basilisk because of its awesome HP reserves.
So tell me, specifically, why the mass driver, shotgun, (ie. the favorite anti-dretch weaponry) and/or (especially) the lucifer cannon is unbalanced. I'd love to do a few 1vs1 rounds of mara vs luci to "prove" my point.